1. Field of the Invention
The present invention relates to display or indicator and control systems, and more particularly to a tactile indicator system for indicating to an operator the achievement of a desired variable exposure condition, such as the proper focus, of a camera or other photographic device. The method and apparatus of the present invention have particular application to various forms of cameras, such as film and video, as well as photographic enlargers, for providing a tactile indication to the camera operator that a proper focus condition or other exposure condition has been achieved. The term camera is used herein and in the claims to include various forms of imaging systems such as film cameras, video cameras, enlargers and the like.
In order to facilitate an understanding of the present invention and applications thereof, the same will be discussed in the context of a photographic film camera for providing a tactile indication that a desired or proper focus condition has been achieved. Other applications of the present concepts will be described.
2. Description of the Prior Art
Various forms of photographic cameras are well known. The more sophisticated cameras include an objective lens system which can be focused on the subject to provide the best photographic image. Typical examples of such cameras are the rangefinder type and the single-lens reflex type. In each instance, the camera operator looks into a viewfinder and adjusts a focusing ring on the lens of the camera to achieve a particular focus condition. The best focus usually is indicated by the coming together of split images. As is apparent to photographers, the focusing operation distracts from composing the picture. Also it should be noted that many cameras having a light metering system include some form of indicator in the viewfinder to indicate when a proper f/stop or shutter speed adjustment has been made in order to achieve a proper exposure. The necessity of viewing these indications likewise is distracting.
In recent years cameras have become more automated. In addition to automatic aperture and/or shutter speed control systems, there now exist on the market several forms of 35 mm cameras which include an autofocus system. These systems comprise a ranging system for determining the distance of the object being photographed, and this system in turn moves the focusing mechanism of the objective lens of the camera. The focusing mechanism may be moved by an electric motor, spring motor, electromagnet, or the like. The ranging systems include those which rely on a sonic ranging signal, those which rely on optical triangulation, such as the infrared ranging systems, and those which rely on image contrast analysis to determine best focus. As is apparent to those skilled in the art, focusing by observing an image or images in the viewfinder of a camera, particularly under low light conditions, is a cumbersome and imprecise operation and, thus, cameras having autofocus features are desirable. However, on the other hand, such cameras with autofocus features include, of necessity, the added complication, weight, and power source required for moving the focusing system of the lens to achieve proper focus. In addition, it is particularly difficult to provide the autofocus feature for cameras which use interchangeable lenses because of the substantial differences in sizes, structures, and the like of such lenses, and the consequent difficulty in providing an appropriate focus adjusting system for a variety of lenses or within each lens.
Considering the patent literature, a number of patents exist disclosing automatic camera systems and several patents exist which illustrate electromagnetic systems in cameras such as for locking a diaphragm-actuating device or lever for locking the diaphragm into a position to enable an appropriate exposure to be made. U.S. Pat. No. 3,922,693 shows an arrangement of this nature using an electromagnet which, when energized, locks a diaphragm-actuating lever in an automatic exposure metering system just prior to exposure of the film. U.S. Pat. No. 4,096,493 includes a discussion of various forms of diaphragm scanning mechanisms and exemplary locking devices therefor. This patent describes a system which allows the photographer to override the automatically selected aperture.
With respect to focusing systems, U.S. Pat. No. 4,171,895 discloses a camera focusing system which locks the focus of the camera at infinity, and the locking system is disengageable for manual focusing. U.S. Pat. No. 3,713,371 describes a camera system with an automatic focusing system responsive to a spacial frequency sensing device. In the system described, the system includes means for shifting the lens from a rest position toward a second position and further means for stopping the first means, and hence the movement of the lens at a position of sharp focus. The system uses a cocking mechanism to move the lens to the infinity focus position when film is advanced, and when it is desired to take a photograph, the lens is moved by a spring until the cocking system is stopped by an electromagnet. Honeywell U.S. Pat. No. 3,945,023 describes a camera rangefinding system of the type referred to earlier as the image contrast analysis type system. This system uses a motor to adjust the focus of the lens system. Polaroid U.S. Pat. No. 3,522,764 illustrates a sonic type camera focusing system. Several forms of autofocus systems are discussed in an article entitled "Autofocus: What's It All About?" which appeared in the June 1980 issue of Modern Photography.